1. Field of the Invention
The present invention relates to systems and methods for analyzing a whole blood sample. More specifically, the present invention relates to a transducer module for use in a blood analysis instrument.
2. Background Art
In diagnosing different illnesses and disease states, it is common to analyze a patient's peripheral blood to differentiate and enumerate the various constituents within the blood, as well as to determine certain parameters or characteristics of those constituents. For example, a whole blood sample (WBS) generally comprises various types of cells (both blood cells and non-blood cells) suspended in a liquid medium or plasma. The blood cells are three basic types, namely, red cells (erythrocytes), white cells (leukocytes), and platelets (thrombocytes). Depending on the level of maturity, red cells are often further classified into three subsets, namely, nucleated red blood cells (NRBCs), reticulated red cells (“retics”), and mature red blood cells (RBCS). Mature white cells fall into one of five different subsets, namely, monocytes, lymphocytes, eosinophils, neutrophils and basophils. Each of the white cell subsets can be further classified into subclasses based on their respective level of maturity, activation or abnormality. Platelets are of three general types, namely, mature platelets, reticulated platelets and large platelets. A thorough blood analysis determines the respective concentrations and relative percents of each of the above cell types and subsets.
Various measurement techniques, alone or in combination, have been implemented in blood analysis instruments to differentiate and enumerate the various constituents in a WBS. For example, direct current (DC) impedance measurements are used to measure the volume of a cell. DC impedance measurements accurately size a cell within an isotonic diluent regardless of the cell type, orientation, maturity, and/or other characteristics. Radio frequency (RF) measurements are used to measure the conductivity of a cell to collect information about cell size and internal structure, including chemical composition and nuclear volume. Further, when a cell is irradiated by a light source, such as a laser beam, the cell scatters light in all directions. Measurements of light scatter at various distinct angles are used to obtain information such as cellular granularity, nuclear lobularity, and cell surface structure. Fluorescence measurements of a stained blood sample have been used for differentiating blood sample constituents. The respective outputs of these measurement techniques are then processed to identify and enumerate the constituents and thereby develop a comprehensive blood analysis report.
U.S. Pat. No. 6,228,652 (“the '652 patent”), which is hereby incorporated by reference in its entirety, discloses, inter alia, a blood analysis instrument. The blood analysis instrument of the '652 patent includes a single transducer for simultaneously measuring the DC impedance, RF conductivity, light scattering, and fluorescence characteristics of blood cells passing one-at-a-time through a cell-interrogation zone in a flow cell. A laser is used for irradiating the cells passing through the cell-interrogation zone. The light scatter from the individual cells is then measured. Simultaneously, the fluorescence of each cell is measured to identify NRBC populations. However, the use of fluorescence to identify NRBCs is relatively expensive due to the high costs of the system components and fluorescent dyes needed to stain the blood sample. Further, in practice, the relatively tight tolerances needed for optical focusing and alignment of the laser within the cell-interrogation zone presents a significant manufacturing challenge.
U.S. Pat. No. 7,208,319 (“the '319 patent”), which is hereby incorporated by reference in its entirety, discloses, inter alia, alternative methods for differentiating NRBCs. The methods of the '319 patent include passing a prepared blood sample through a flow cell, irradiating the individual cells of the sample as they pass through the cell-interrogation zone of the flow cell, and measuring combinations of DC impedance, axial light loss, low angle light scatter, and median angle light scatter.
Additional systems and methods are described in U.S. Pat. Nos. 5,125,737; 5,616,501; 5,874,311; 6,232,125; 7,008,792; and 7,208,319, the disclosures of which are hereby incorporated by reference in their entireties.